An individual-based model, EcoSim, was employed to investigate if specialized resource use could promote sympatric speciation. Prey individuals in the original version of EcoSim were supplied with a single primary food resource. A dual resource version with different food resources (Food 1 and Food 2) was also developed to create favorable conditions for the emergence of specialized food consumption among prey individuals. The single resource version was used as the control to determine the impact of the presence of multiple food resources on the occurrence of sympatric speciation. Each unit of Food 2 contained a higher amount of energy than Food 1, and Food 1 was more accessible than Food 2. Initially, prey individuals mostly fed on Food 1. However, after the emergence of food specialization, the consumption rate of Food 2 significantly exceeded the consumption rate of Food 1; although prey individuals more frequently encountered Food 1. While sympatric speciation was observed in the dual resource version runs, we could not identify any sympatric species in the single resource version runs. Machine learning techniques were also employed to identify the most influential initial conditions leading to sympatric speciation. According to the obtained results, in most lineages sympatric speciation occurred at the beginning of the food specialization process. When the lineage had a high special diversity, the lineage needed two different criteria to diverge sympatrically: possessing high genetic diversity and a large population size. In support of previous findings, this study demonstrated that the most accurate determination of initial conditions leading to sympatric speciation can be obtained from lineages that are at the beginning of the divergence process. In conclusion, this study indicated that divergent foraging behavior could potentially lead to the sympatric emergence of new How to cite this paper: Pour, M.K., Bandehbahman, S., Gras, R. and Cristescu, M.E.

Polychlorinated biphenyls (PCBs) are classified as one the most extremely regulated anthropogenic contaminants and they have been deeply probed in aquatic ecosystems. However, there is very limited understanding of the population level effects of exposure to PCBs on terrestrial animal species and this has been unanimously indicated as a critical gap in ecological risk assessment. To bridge this information gap, we integrated an individual-based model (IBM) framework into toxicokinetics resulting in a deeper ecological insight to simulate the accumulation of a hypothetical PCB in a terrestrial three-level food chain at the population level. We then validated our simulated system utilizing the observed field bioaccumulation factors in a well-studied terrestrial preypredator, caribou-wolf. Key findings of the present study indicate that in a PCBcontaminated environment, where all food sources contain some amount of contaminants, producing more offspring results in lower toxic concentration in herbivores (prey) and higher concentration in carnivores (predator). Our novel contribution in this work is that we have achieved a validated system that enables us to investigate toxicokinetics in any animal species involved in a prey-predation interaction by providing lipid, non-lipid, and water fractions in their bodies. Additionally, we demonstrated how using IBM modelling approach could facilitate ecological risk assessment by offering detailed information of generations spanning as many years as required.

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